Infrared optical masking or discrimination is a technique used by a defender to distinguish reentry vehicles from decoys by detecting the infrared signature of an object and comparing it to the temperature/time profiles of a known reentry vehicle. Presently, decoys are made by matching their temperature/time profiles using heaters or pyrotechnic techniques under cooling environments. This requires power supplies, wiring and some type of transducer which increase the size, weight and complexity of the decoy and generally encumber its design. Under heating environments, means for cooling are required, which are even more cumbersome, especially for integration into the skin of an aerospace vehicle. Extremes of cold and heat must be accounted for in exo-atmospheric applications where the objects pass from light to dark through the sun's terminator and alternately face deep space or the sun's rays. These environments establish the overall temperature range limits over which matching is desired. The matching must occur for any combinations and values of heating and cooling that can occur.
The defender is assumed to have multi-color infrared detection capability. Because of this, it is necessary for the decoy to match the reentry vehicle in size, shape and actual surface temperature profiles. The decoy top surface must match the reentry vehicle in detailed surface radiative properties (in all directions from surface normals, and over all wavelengths from far infrared to solar). A special thin top sheet of the decoy matches these radiative characteristics. These considerations require that the passive decoy, in matching the reentry vehicle, experience the same heating or cooling fluxes, and therefore must have the same overall heat capacity. In order to use a light-weight decoy the fundamental objective then must be to use a decoy structure having an effective specific heat much larger than that of the reentry vehicle.